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使用Redis做MyBatis的二级缓存
1. 介绍
使用mybatis时可以使用二级缓存提高查询速度，进而改善用户体验。
使用redis做mybatis的二级缓存可是内存可控<如将单独的服务器部署出来用于二级缓存>，管理方便。
2. 使用思路
2.1 配置redis.xml 设置redis服务连接各参数
2.1 在配置文件中使用 <setting> 标签，设置开启二级缓存；
2.2 在mapper.xml 中使用<cache type="com.demo.RedisCacheClass" /> 将cache映射到指定的RedisCacheClass类中；
2.3 映射类RedisCacheClass 实现 MyBatis包中的Cache类，并重写其中各方法；
在重写各方法体中，使用redisFactory和redis服务建立连接，将缓存的数据加载到指定的redis内存中(putObject方法)或将redis服务中的数据从缓存中读取出来(getObject方法)；
在redis服务中写入和加载数据时需要借用spring-data-redis.jar中JdkSerializationRedisSerializer.class中的序列化(serialize)和反序列化方法(deserialize),此为包中封装的redis默认的序列化方法；
2.4 映射类中的各方法重写完成后即可实现mybatis数据二级缓存到redis服务中；
3. 代码实践
3.1 配置redis.xml
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.0.xsd" > <!-- enable autowire --> <context:annotation-config /> <task:annotation-driven/> <context:component-scan base-package="demo.util,demo.salesorder,demo.person" /> <!-- Configures the @Controller programming model 必须加上这个，不然请求controller时会出现no mapping url错误--> <mvc:annotation-driven /> <!-- 引入数据库配置文件 --> <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>classpath:sysconfig/jdbc.properties</value> <value>classpath:sysconfig/redis.properties</value> </list> </property> </bean> <!-- JDBC --> <bean id="defaultDataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" p:driverClassName="${jdbc.driverClassName}" p:url="${jdbc.databaseurl}" p:username="${jdbc.username}" p:password="${jdbc.password}" > <property name="maxActive"> <value>${jdbc.maxActive}</value> </property> <property name="initialSize"> <value>${jdbc.initialSize}</value> </property> <property name="maxWait"> <value>${jdbc.maxWait}</value> </property> <property name="maxIdle"> <value>${jdbc.maxIdle}</value> </property> <property name="minIdle"> <value>${jdbc.minIdle}</value> </property> <!-- 只要下面两个参数设置成小于8小时(MySql默认)，就能避免MySql的8小时自动断开连接问题 --> <property name="timeBetweenEvictionRunsMillis"> <value>18000000</value> </property><!-- 5小时 --> <property name="minEvictableIdleTimeMillis"> <value>10800000</value> </property><!-- 3小时 --> <property name="validationQuery"> <value>SELECT 1</value> </property> <property name="testOnBorrow"> <value>true</value> </property> </bean> <!-- define the SqlSessionFactory --> <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="defaultDataSource" /> <property name="typeAliasesPackage" value="demo.salesorder,demo.person" /> <!-- 可以单独指定mybatis的配置文件，或者写在本文件里面。 用下面的自动扫描装配(推荐)或者单独mapper --> <property name="configLocation" value="classpath:sysconfig/mybatis-config.xml" /> </bean> <!-- 自动扫描并组装MyBatis的映射文件和接口--> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <property name="basePackage" value="demo.*.data" /> <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property> </bean> <!-- JDBC END --> <!-- redis数据源 --> <bean id="poolConfig" class="redis.clients.jedis.JedisPoolConfig"> <property name="maxIdle" value="${redis.maxIdle}" /> <property name="maxTotal" value="${redis.maxActive}" /> <property name="maxWaitMillis" value="${redis.maxWait}" /> <property name="testOnBorrow" value="${redis.testOnBorrow}" /> </bean> <!-- Spring-redis连接池管理工厂 --> <bean id="jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory"> <property name="hostName" value="${redis.host}" /> <property name="port" value="${redis.port}" /> <property name="password" value="${redis.pass}" /> <property name="timeout" value="${redis.timeout}" /> <property name="poolConfig" ref="poolConfig" /> </bean> <!-- 使用中间类解决RedisCache.jedisConnectionFactory的静态注入，从而使MyBatis实现第三方缓存 --> <bean id="redisCacheTransfer" class="demo.redis.RedisCacheTransfer"> <property name="jedisConnectionFactory" ref="jedisConnectionFactory"/> </bean> <bean class="demo.util.UTF8StringBeanPostProcessor"></bean> </beans>
3.2 mybatis.xml 配置开启二级缓存
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <!-- 配置mybatis的缓存，延迟加载等等一系列属性 --> <settings> <!-- 全局映射器启用缓存 *主要将此属性设置完成即可--> <setting name="cacheEnabled" value="true"/> <!-- 查询时，关闭关联对象即时加载以提高性能 --> <setting name="lazyLoadingEnabled" value="false"/> <!-- 对于未知的SQL查询，允许返回不同的结果集以达到通用的效果 --> <setting name="multipleResultSetsEnabled" value="true"/> <!-- 设置关联对象加载的形态，此处为按需加载字段(加载字段由SQL指 定)，不会加载关联表的所有字段，以提高性能 --> <setting name="aggressiveLazyLoading" value="true"/> </settings> </configuration>
3.3 在mapper.xml中映射缓存类RedisCacheClass
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="demo.person.data.UserMapper"> <cache type="demo.redis.cache.RedisCache"/> <!-- *映射语句 --> <select id="getPersonList" parameterType="map" resultType="Person"> select * from person <where> 1=1 <if test="user_name!=null"> and user_name=#{user_name} </if> </where> </select> <insert id="addPerson" parameterType="Person" keyProperty="id" useGeneratedKeys="true"> insert into person( login_id, user_name, gender, birthday, remark )values( #{login_id}, #{user_name}, #{gender}, #{birthday}, #{remark} ) </insert> </mapper>
3.4 实现Mybatis中的Cache接口
Cache.class源码：
/* * Copyright 2009-2012 the original author or authors. * http://www.apache.org/licenses/LICENSE-2.0*/ package org.apache.ibatis.cache; import java.util.concurrent.locks.ReadWriteLock; public interface Cache { String getId(); int getSize(); void putObject(Object key, Object value); Object getObject(Object key); Object removeObject(Object key); void clear(); ReadWriteLock getReadWriteLock(); }
RedisCache.java
package demo.redis.cache; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; import org.apache.ibatis.cache.Cache; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.data.redis.connection.jedis.JedisConnection; import org.springframework.data.redis.connection.jedis.JedisConnectionFactory; import org.springframework.data.redis.serializer.JdkSerializationRedisSerializer; import org.springframework.data.redis.serializer.RedisSerializer; import redis.clients.jedis.exceptions.JedisConnectionException; public class RedisCache implements Cache //实现类 { private static final Logger logger = LoggerFactory.getLogger(RedisCache.class); private static JedisConnectionFactory jedisConnectionFactory; private final String id; /** * The {@code ReadWriteLock}. */ private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); public RedisCache(final String id) { if (id == null) { throw new IllegalArgumentException("Cache instances require an ID"); } logger.debug("MybatisRedisCache:id=" + id); this.id = id; } @Override public void clear() { JedisConnection connection = null; try { connection = jedisConnectionFactory.getConnection(); //连接清除数据 connection.flushDb(); connection.flushAll(); } catch (JedisConnectionException e) { e.printStackTrace(); } finally { if (connection != null) { connection.close(); } } } @Override public String getId() { return this.id; } @Override public Object getObject(Object key) { Object result = null; JedisConnection connection = null; try { connection = jedisConnectionFactory.getConnection(); RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer(); //借用spring_data_redis.jar中的JdkSerializationRedisSerializer.class result = serializer.deserialize(connection.get(serializer.serialize(key))); //利用其反序列化方法获取值 } catch (JedisConnectionException e) { e.printStackTrace(); } finally { if (connection != null) { connection.close(); } } return result; } @Override public ReadWriteLock getReadWriteLock() { return this.readWriteLock; } @Override public int getSize() { int result = 0; JedisConnection connection = null; try { connection = jedisConnectionFactory.getConnection(); result = Integer.valueOf(connection.dbSize().toString()); } catch (JedisConnectionException e) { e.printStackTrace(); } finally { if (connection != null) { connection.close(); } } return result; } @Override public void putObject(Object key, Object value) { JedisConnection connection = null; try { logger.info(">>>>>>>>>>>>>>>>>>>>>>>>putObject:"+key+"="+value); connection = jedisConnectionFactory.getConnection(); RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer(); //借用spring_data_redis.jar中的JdkSerializationRedisSerializer.class connection.set(serializer.serialize(key), serializer.serialize(value)); //利用其序列化方法将数据写入redis服务的缓存中 } catch (JedisConnectionException e) { e.printStackTrace(); } finally { if (connection != null) { connection.close(); } } } @Override public Object removeObject(Object key) { JedisConnection connection = null Object result = null; try { connection = jedisConnectionFactory.getConnection(); RedisSerializer<Object> serializer = new JdkSerializationRedisSerializer(); result =connection.expire(serializer.serialize(key), 0); } catch (JedisConnectionException e) { e.printStackTrace(); } finally { if (connection != null) { connection.close(); } } return result; } public static void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) { RedisCache.jedisConnectionFactory = jedisConnectionFactory; } }
4. 总结
通过重写Cache类中的方法，将mybatis中默认的缓存空间映射到redis空间中。
使用Redis做MyBatis的二级缓存
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